I migrated from TextMate about a week ago and I've been loving Sublime Text 2 so far. However there is one thing that I miss, its a simple documention tooltip which shows the documentation of the current highlighted function or the function where my cursor is. This tooltip is available in the PHP bundle.

Sublime Text 2 doesn't currently support this kind of tooltips, but it's on the list. I spoke with Jon about it a couple months ago. Hopefully we get these kind of tooltips soon, as some plugins really could use them